1. Field of the Invention
This invention relates to a temperature-type expansion valve installed to an air conditioning apparatus such as a car air conditioner, for controlling a flow rate of a refrigerant supplied to an evaporator in accordance with the temperature of the refrigerant.
2. Description of the Related Art
A temperature-type expansion valve of this kind described in Japanese Unexamined Patent Publication No. 2002-310538, for example, includes a prismatic valve housing, a first passage formed inside this valve housing for the passage of a high pressure refrigerant, a valve chamber formed inside this passage, a second passage formed inside the valve housing in parallel with the first passage, for the passage of the refrigerant sent to the evaporator side, a throttle passage into which a valve seat member for communicating the valve chamber and the second passage is pushed, a spherical valve body arranged in opposition inside the throttle passage, a third passage for the passage of the refrigerant sent from the evaporator side, and an operation rod for sensing the temperature of the refrigerant passing through the third passage and driving the valve body.
The valve seat member described above is fixed to the throttle passage under the state where it is installed in advance between the valve body and the operation rod. The operation rod has a small diameter portion inserted into the valve seat member and the spherical valve body is fixed to the distal end of the small diameter portion. In consequence, the open area of the throttle passage can be adjusted by the displacement of the valve body.
However, Japanese Unexamined Patent Publication No. 2002-310538 described above employs a complicated construction, as the flow rate regulating function, in which the rod-like operation rod, the spherical valve body, the tubular valve seat member, and so forth, are constituted integrally beforehand. Among these members, the valve seat member is fitted to the small diameter portion of the operation rod but because a gap is secured between the valve seat member and the small diameter portion, there remains the problem of centering when the valve seat member is fixed by press-fitting to the throttle passage by using the operation rod, for example.
In this construction, the valve body and the operation rod are fixed. When the operation rod is welded to the valve body, for example, a variation occurs in the length of the operation rod owing to the penetration of welding. When the valve seat member is fixed by press-fitting to the throttle passage by using such an operation rod, deformation develops at the end portion of the operation rod, so that the accuracy of the flow rate control by the expansion valve drops.